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<h1>rsyslog vs. syslog-ng</h1>
<p><small><i>Written by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a>
(2008-05-06)</i></small></p>
<p>We have often been asked about a comparison sheet between
rsyslog and syslog-ng. Unfortunately, I do not know much about
syslog-ng, I did not even use it once. Also, there seems to be no
comprehensive feature sheet available for syslog-ng (that recently
changed, see below). So I started this
comparison, but it probably is not complete. For sure, I miss some
syslog-ng features. This is not an attempt to let rsyslog shine more
than it should. I just used the <a href="features.html">rsyslog
feature sheet</a> as a starting point, simply because it was
available. If you would like to add anything to the chart, or correct
it, please simply <a href="mailto:rgerhards@adiscon.com">drop
me a line</a>. I would love to see a real honest and up-to-date
comparison sheet, so please don't be shy ;)</p>
<table border="1">
<tbody>
<tr>
<td valign="top"><b>Feature</b></td>
<td valign="top"><b>rsyslog</b></td>
<td valign="top"><b>syslog-ng</b></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Input Sources</b><br>
</td>
</tr>
<tr>
<td valign="top">UNIX domain socket</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">UDP</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">TCP</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top"><a href="http://www.librelp.com">RELP</a></td>
<td valign="top">yes</td>
<td valign="top">no</td>
<td></td>
</tr>
<tr>
<td valign="top">RFC 3195/BEEP</td>
<td valign="top">yes (via <a href="im3195.html">im3195</a>)</td>
<td valign="top">no</td>
<td></td>
</tr>
<tr>
<td valign="top">kernel log</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">file</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">mark message generator as an
optional input</td>
<td valign="top">yes</td>
<td valign="top">no (?)</td>
<td></td>
</tr>
<tr>
<td valign="top">Windows Event Log</td>
<td valign="top">via <a href="http://www.eventreporter.com">EventReporter</a>
or <a href="http://www.mwagent.com">MonitorWare Agent</a>
(both commercial software)</td>
<td valign="top">via separate Windows agent, paid
edition only</td>
</tr>
<tr>
<td colspan="3" valign="top"><b><br>
Network (Protocol) Support</b><br>
</td>
</tr>
<tr>
<td valign="top">support for (plain) tcp based syslog</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">support for GSS-API</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">ability to limit the allowed
network senders (syslog ACLs)</td>
<td valign="top">yes</td>
<td valign="top">yes (?)</td>
</tr>
<tr>
<td valign="top">support for syslog-transport-tls
based framing on syslog/tcp connections</td>
<td valign="top">yes</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">udp syslog</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">syslog over RELP<br>
truly reliable message delivery (<a href="http://blog.gerhards.net/2008/05/why-you-cant-build-reliable-tcp.html">Why
is plain tcp syslog not reliable?</a>)</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">on the wire (zlib) message
compression</td>
<td valign="top">yes</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">support for receiving messages via
reliable <a href="http://www.monitorware.com/Common/en/glossary/rfc3195.php">RFC
3195</a> delivery</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">support for <a href="rsyslog_tls.html">TLS/SSL-protected
syslog</a> </td>
<td valign="top"><a href="rsyslog_tls.html">natively</a> (since 3.19.0)<br><a href="rsyslog_stunnel.html">via
stunnel</a></td>
<td valign="top">via stunnel<br>
paid edition natively</td>
</tr>
<tr>
<td valign="top">support for IETF's new syslog-protocol draft</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">support for IETF's new syslog-transport-tls draft</td>
<td valign="top">yes<br>(since 3.19.0 - world's first implementation)</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">support for IPv6</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">native ability to send SNMP traps</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">ability to preserve the original
hostname in NAT environments and relay chains</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Message Filtering</b><br>
</td>
</tr>
<tr>
<td valign="top">Filtering for syslog facility and
priority</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for hostname</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for application</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for message contents</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">Filtering for sending IP address</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">ability to filter on any other message
field not mentioned above (including substrings and the like)</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td>support for complex filters, using full boolean algebra
with and/or/not operators and parenthesis</td>
<td>yes</td>
<td>yes</td>
</tr>
<tr>
<td>Support for reusable filters: specify a filter once and
use it in multiple selector lines</td>
<td>no</td>
<td>yes</td>
</tr>
<tr>
<td>support for arbritrary complex arithmetic and string
expressions inside filters</td>
<td>yes</td>
<td>no</td>
</tr>
<tr>
<td valign="top">ability to use regular expressions
in filters</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">support for discarding messages
based on filters</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">ability to filter out messages based on sequence of appearing</td>
<td valign="top">yes (starting with 3.21.3)</td>
<td valign="top">no</td>
<td></td>
</tr>
<tr>
<td valign="top">powerful BSD-style hostname and
program name blocks for easy multi-host support</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Supported Database Outputs</b><br>
</td>
</tr>
<tr>
<td valign="top">MySQL</td>
<td valign="top"><a href="rsyslog_mysql.html">yes</a>
(native ommysql,&nbsp;<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">yes (via libdibi)</td>
</tr>
<tr>
<td valign="top">PostgreSQL</td>
<td valign="top">yes (native ompgsql,&nbsp;<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">yes (via libdibi)</td>
</tr>
<tr>
<td valign="top">Oracle</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">yes (via libdibi)</td>
</tr>
<tr>
<td valign="top">SQLite</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">yes (via libdibi)</td>
</tr>
<tr>
<td valign="top">Microsoft SQL (Open TDS)</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">Sybase (Open TDS)</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">Firebird/Interbase</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">Ingres</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">mSQL</td>
<td valign="top">yes (<a href="omlibdbi.html">omlibdbi</a>)</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Enterprise Features</b><br>
</td>
</tr>
<tr>
<td valign="top">support for on-demand on-disk
spooling of messages</td>
<td valign="top">yes</td>
<td valign="top">paid edition only</td>
</tr>
<tr>
<td valign="top">ability to limit disk space used
by spool files</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">each action can use its own,
independant
set of spool files</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">different sets of spool files can
be placed on different disk</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">ability to process spooled
messages only during a configured timeframe (e.g. process messages only
during off-peak hours, during peak hours they are enqueued only)</td>
<td valign="top"><a href="http://wiki.rsyslog.com/index.php/OffPeakHours">yes</a><br>
(can independently be configured for the main queue and each action
queue)</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">ability to configure backup
syslog/database servers </td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td>Professional Support</td>
<td><a href="professional_support.html">yes</a></td>
<td>yes</td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Config File</b><br>
</td>
</tr>
<tr>
<td valign="top">config file format</td>
<td valign="top">compatible to legacy syslogd but
ugly</td>
<td valign="top">clean but not backwards compatible</td>
</tr>
<tr>
<td valign="top">ability to include config file from
within other config files</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td height="25" valign="top">ability to
include all config files
existing in a specific directory</td>
<td height="25" valign="top">yes</td>
<td height="25" valign="top">no</td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Extensibility</b><br>
</td>
</tr>
<tr>
<td valign="top">Functionality split in separately
loadable
modules</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td valign="top">Support for third-party input
plugins</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
</tr>
<tr>
<td valign="top">Support for third-party output
plugins</td>
<td valign="top">yes</td>
<td valign="top">no</td>
</tr>
<tr>
<td colspan="3" valign="top"><br>
<b>Other Features</b><br>
</td>
</tr>
<tr>
</tr>
<tr>
<td valign="top">ability to generate file names and
directories (log targets) dynamically</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">control of log output format,
including ability to present channel and priority as visible log data</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr><td valign="top">native ability to send mail messages</td>
<td valign="top">yes (<a href="ommail.html">ommail</a>, introduced in 3.17.0)</td>
<td valign="top">no (only via piped external process)</td>
</tr>
<tr>
<td valign="top">good timestamp format control; at a
minimum, ISO 8601/RFC 3339 second-resolution UTC zone</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">ability to reformat message
contents and work with substrings</td>
<td valign="top">yes</td>
<td valign="top">I think yes</td>
</tr>
<tr>
<td valign="top">support for log files larger than
2gb</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">support for log file size
limitation
and automatic rollover command execution</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">support for running multiple
syslogd instances on a single machine</td>
<td valign="top">yes</td>
<td valign="top">? (but I think yes)</td>
</tr>
<tr>
<td valign="top">ability to execute shell scripts on
received messages</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">ability to pipe messages to a
continously running program</td>
<td valign="top">no</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">massively multi-threaded for
tomorrow's multi-core machines</td>
<td valign="top">yes</td>
<td valign="top">no (only multithreaded with
database destinations)</td>
</tr>
<tr>
<td valign="top">ability to control repeated line
reduction ("last message repeated n times") on a per selector-line basis</td>
<td valign="top">yes</td>
<td valign="top">yes (?)</td>
</tr>
<tr>
<td valign="top">supports multiple actions per
selector/filter condition</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
<td></td>
</tr>
<tr>
<td valign="top">web interface</td>
<td valign="top"><a href="http://www.phplogcon.org">phpLogCon</a><br>
[also works with <a href="http://freshmeat.net/projects/php-syslog-ng/">
php-syslog-ng</a>]</td>
<td valign="top"><a href="http://freshmeat.net/projects/php-syslog-ng/">
php-syslog-ng</a></td>
</tr>
<tr>
<td valign="top">using text files as input source</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">rate-limiting output actions</td>
<td valign="top">yes</td>
<td valign="top">yes</td>
</tr>
<tr>
<td valign="top">discard low-priority messages under
system stress</td>
<td valign="top">yes</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td height="43" valign="top">flow control
(slow down message reception when system is busy)</td>
<td height="43" valign="top">yes (advanced,
with multiple ways to slow down inputs depending on individual input
capabilities, based on watermarks)</td>
<td height="43" valign="top">yes (limited?
"stops accepting messages")</td>
</tr>
<tr>
<td valign="top">rewriting messages</td>
<td valign="top">yes</td>
<td valign="top">yes (at least I think so...)</td>
</tr>
<tr>
<td valign="top">output data into various formats</td>
<td valign="top">yes</td>
<td valign="top">yes (looks somewhat limited to me)</td>
</tr>
<tr>
<td valign="top">ability to control "message
repeated n times" generation</td>
<td valign="top">yes</td>
<td valign="top">no (?)</td>
</tr>
<tr>
<td valign="top">license</td>
<td valign="top">GPLv3 (GPLv2 for v2 branch)</td>
<td valign="top">GPL (paid edition is closed source)</td>
</tr>
<tr>
<td valign="top">supported platforms</td>
<td valign="top">Linux, BSD, anecdotical seen on
Solaris; compilation and basic testing done on HP UX</td>
<td valign="top">many popular *nixes</td>
</tr>
<tr>
<td valign="top">DNS cache</td>
<td valign="top">no</td>
<td valign="top">yes</td>
</tr>
</tbody>
</table>
<p>While the <span style="font-weight: bold;">rsyslog</span>
project was initiated in 2004, it <span style="font-weight: bold;">is
build on the main author's (Rainer Gerhards) 12+ years of
logging&nbsp;experience</span>. Rainer, for example, also
wrote the first <a href="http://www.winsyslog.com/Common/en/News/WinSyslog-1996-03-31.php">Windows
syslog server</a> in early 1996 and invented the <a href="http://www.eventreporter.com/Common/en/News/EvntSLog-1997-03-23.php">eventlog-to-syslog</a>
class of applications in early 1997. He did custom logging development
and consulting even before he wrote these products. Rsyslog draws on
that vast experience and sometimes even on the code.</p>
<p>Based on a discussion I had, I also wrote about the <b>political
argument why it is good to have another strong syslogd besides syslog-ng</b>.
You may want to read it at my blog at "<a href="http://rgerhards.blogspot.com/2007/08/why-does-world-need-another-syslogd.html">Why
does the world need another syslogd?</a>".</p>
<p>Balabit, the vendor of syslog-ng, has just recently done a
feature sheet. I have not yet been able to fully work through it. In
the mean time, you may want to read it in parallel. It is available at
<a href="http://www.balabit.com/network-security/syslog-ng/features/detailed/">Balabit's
site</a>.</p>
<p>[<a href="manual.html">manual index</a>]
[<a href="rsyslog_conf.html">rsyslog.conf</a>]
[<a href="http://www.rsyslog.com/">rsyslog site</a>]</p>
<p><font size="2">This documentation is part of the
<a href="http://www.rsyslog.com/">rsyslog</a> project.<br>
Copyright &copy; 2008 by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and
<a href="http://www.adiscon.com/">Adiscon</a>. Released under the GNU GPL
version 2 or higher.</font></p>

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